Extensible stand



FIG. 1 is a perspective view of an extensible stand showing my design.

FIG. 2 is a front view thereof.

FIG. 3 is a back view thereof.

FIG. 4 is a side view thereof.

FIG. 5 is a bottom view thereof; and,

FIG. 6 is a top view thereof. 

The ornamental design for an extensible stand, as shown. 